Cornea of ​​the eye



English: corneal crafting


The cornea (Cornea) covers the anterior segment of the eye. It is about 550 micrometers to 700 micrometers thin, transparent, collagen-containing layer that cannot be seen with the naked eye. It serves to protect the eyeball and refract the incident light rays.

Structure of the cornea

The cornea consists of several layers (structure). The multilayered corneal epithelium protects the corneal surface and fends off germs.
Together with the tear fluid, it forms the smooth, refractive surface of the optical system. The basal epithelial cells are anchored in a basement membrane, which is embedded in the so-called Bowman membrane (a thicker and coarse layer) and contributes to the stability of the cornea.

The corneal stroma is formed by parallel layers of collagenous fibers and is transparent due to its regular and narrow lattice structure.

On the inside of the cornea / Cornea is the single-layer corneal endothelium. Its basement membrane is also crossed by elastic fibers and is called the descement membrane. The corneal endothelium seals the corneal stroma from the aqueous humor. Any liquid which has penetrated is pumped back into the anterior chamber.

The cornea is unable to regenerate itself after deeper injuries.The structure of the cornea remains permanently damaged.

Illustration: Horizontal section through the left eyeball, seen from below
  1. Cornea - Cornea
  2. Dermis - Sclera
  3. Iris - iris
  4. Radiation body - Corpus ciliary
  5. Choroid - Choroid
  6. Retina - retina
  7. Anterior chamber of the eye -
    Camera anterior
  8. Chamber angle -
    Angulus irodocomealis
  9. Posterior chamber of the eye -
    Camera posterior
  10. Eye lens - Lens
  11. Vitreous - Corpus vitreum
  12. Yellow spot - Macula lutea
  13. Blind spot -
    Discus nervi optici
  14. Optic nerve (2nd cranial nerve) -
    Optic nerve
  15. Main line of sight - Axis opticus
  16. Axis of the eyeball - Axis bulbi
  17. Lateral rectus eye muscle -
    Lateral rectus muscle
  18. Inner rectus eye muscle -
    Medial rectus muscle

You can find an overview of all Dr-Gumpert images at: medical illustrations

Functions of the cornea

First of all, the Cornea as a front lens, i.e. it contributes to the imaging of the image on the retina with its own refractive power. Its refractive power is 43 diopters. In addition to its contribution to vision, the cornea also has a protective function. In this way, it can cushion the intraocular pressure generated in the eye. The cornea is a very important part of the optical apparatus that cannot be done without.

Corneal diseases: astigmatism

An astigmatism is also called astigmatism designated. This is a harmless and very widespread corneal anomaly that can be observed in around 70% of all people who wear glasses.
Literally translated, astigmatism means something like "pointlessness". In German, astigmatism is also called "Astuteness“.
A normal and healthy cornea has a uniform curvature in all directions of its radius.
In people with astigmatism, which is usually congenital and which does not recede in the course of life, the cornea is now slightly more curved in one direction than in the other. As a result, the light rays hitting the eye are no longer shown as punctiform, but rather as lines on the retina.
The horizontal rays of light are refracted more than the vertical ones. As a result, the rays do not come together in a single sharp focus on the retina. Instead, two different rod-shaped focal lines are created: the image appears slightly distorted.
This explains the term “astigmatism”.
Astigmatism can very often be observed in combination with other refractive errors of the eye, for example in combination with myopia or farsightedness.
Once the astigmatism is recognized and diagnosed, it can be easily remedied with glasses, contact lenses or refractory surgery on the cornea.

Read more about the topic here: Astigmatism.

Inflammation of the cornea

Inflammation of the cornea is also known as keratitis. It can have many different causes, but most of the time it is an infection. Various pathogens such as bacteria or viruses, but also fungi can occur here.

Non - infectious causes can be, for example, strong UV light or insufficient eyelid closure, which leads to the cornea drying out.
Because the cornea of ​​the eye is very sensitive, corneal inflammation can cause severe pain. In addition, there is often a reddening of the eyes, which can secrete secretions or tears. This is especially the case if the conjunctiva is also inflamed.

Corneal inflammation is a serious disease that should be treated. Otherwise the cornea may become cloudy or scarred.
The most common form of corneal inflammation is bacterial infection. It can occur when wearing dirty contact lenses. Any pathogens adhering to it can affect the eye. A purulent secretion is typical of bacterial inflammation. Bacterial corneal inflammation is considered an emergency as it can go as far as perforating the protective cornea.

Find out more about the topic here: Corneal inflammation.

What do you do if you injure your cornea?

First aid for an injury to the cornea always depends on the type of injury. A common cause of corneal injuries are foreign bodies, such as those that can arise from improper grinding or drilling. If such foreign objects penetrate the cornea, it can be very difficult to determine the severity of the injury. Therefore, one should consult an ophthalmologist if the cornea is injured. This can safely remove any foreign body that may still be in the eye.
In addition, an antibiotic is often given as an eye drop, for example. This is especially necessary if dirt has been brought into the eye with the foreign body or if there is a defect in the cornea through which pathogens can penetrate.

But not only mechanical force can damage the cornea. Many harsh chemicals can also damage the cornea. The first aid in this case is to rinse the eye thoroughly with clean water. This should be done as soon as possible.
Many workplaces also have special devices for rinsing the eye. In addition, an ophthalmologist should be consulted immediately.

You can find more here on the topic: Injuries to the eye.

Corneal detachment

The cornea of ​​the eye forms the front wall of the eyeball. Behind her is the anterior chamber of the eye. This is the space between the cornea and the iris. The cornea does not lie on any tissue from which it could detach. Not to be confused with a detachment of the cornea is a detachment of the retina, which, however, is located in a different place in the eye.

The cornea of ​​the eye consists of several different layers of tissue. On the inside of the cornea is a thin layer of cells, which is also called Endothelium referred to as. In the Fuchs endothelial dystrophy With increasing age, these endothelial cells perish. This presumably has, among other things, hereditary causes. The endothelial cells are required for the metabolism of the cornea. As a result, the cornea swells. Cell layers can stand out here. The cornea can also become cloudy.
Gaps within the cornea are also conceivable as a result of injuries to the eye.

Corneal transplant

Corneal transplantation can be performed if corneal diseases severely limit the eye's vision, or corneal diseases that cannot be controlled otherwise. This involves removing the patient's cornea and replacing it with a donor cornea. It is possible to replace the entire cornea or individual sections. It is a corpse donation, so the cornea is only removed after the donor's death.

The cornea is usually not supplied with blood. This has several advantages in corneal transplantation. Since the cells of the cornea do not depend on blood flow, they remain viable for days after the donor's death and can theoretically be transplanted. In addition, the recipient's immune system usually does not react to the foreign tissue because it does not come into contact with it due to the lack of blood vessels.

Read more about the topic here: Corneal transplant